Such an assembly is known in the art and is shown by way of example in FIG. 4. The assembly consists of a dosing part 38 and a supply part 39. The supply part 39 comprises an outlet 40, which is sealed by means of a sealing element 41, which is circumferentially connected to the end of the outlet 40 by means of a weld 42. Note that the parts shown in FIG. 4 are circularly symmetrical in relation to a longitudinal axis through the centre of the illustrated section. The dosing part comprises a dose container 45, in which a dose can be received. The dose container 45 has a wall 46, which is so configured that it can be received in a corresponding wall 47 of the supply part 39.
An outer wall of the dosing part consists of a first wall part 48 and a second wall part 49, which annularly surround the wall 46 of the dose container 45. The first part 48 of the outer wall of the dose container is connected to the second part 49 of the outer wall by means of a multitude of concentrically arranged welds 50. The welds 50 are so dimensioned that the welds can be easily broken by exerting a force on the wall parts 48 and 49.
The assembly is sealed by filling the dose container 45 of the dosing part and sliding the wall 47 of the supply part over the wall 46 of the dosing part 38. The supply part is moved into the dosing part until the receiving part 48 that concentrically surrounds the wall 47 of the supply part abuts against the welds 50 of the dosing part. The end 51 of the wall 47 will slide into the space 53 between the wall 46 of the dose container and the second wall part 49 thereof. The end of the supply part 39, consisting of the outlet 40, is now moved into the filling opening of a correspondingly shaped container (not shown). The supply part 39 is moved into said opening until the edges of the filling opening of the container (not shown) abut against the side 56 of the receiving part 58 of the supply part 39.
The dose that is present in the dose container 45 is transferred in the following manner. When a force is exerted on the assembly via the rear side 52 of the dosing part 38, the welds 50 will be broken by the receiving part 58, as a result of which the second wall part 49 of the dosing part will become detached from the first wall part 48. The force being exerted causes the detached part of the dosing part 38, consisting of the second wall part 49, the rear side 52 and the dose container 46, to move further into the receiving part 58, and the end 55 of the wall 46 of the dose container will perforate the concentric weld 42 of the sealing element 41 of the outlet 40, as a result of which the outlet 40 is opened, so that the dose will flow into the container. In the container, the dose will mix with the container substance that is already present in the container.
A drawback of the prior art assembly as described above is that fluid may remain behind in the dose container 45, for example on the walls and in the corners thereof. In addition, it is not possible to mix the residue of the dose that has remained behind in the dose conveyor 45 with a container substance that is present in the container yet, in particular if the weld 42 has not been completely broken by the end 55 of the wall 46 of the dose container 45. In practice it has become apparent that usually the amount of air that is present in the dose container cannot move out of the dose container 45 if the weld 42 has not been completely broken, so that a barrier is formed, which prevents the dose from flowing back into the dose container. Another problem is that the wall of the dose container shoots through into the container as a result of the weld 42 being broken, forming a physical barrier at that location, which prevents the dose from flowing back.
Another drawback of the prior art assembly is that a relatively large force is required for perforating the weld 42. This has a negative effect on the functionality of the assembly and, in addition, increases the risk of accidents.
Another possibility of mixing a dose with a container substance is to use a pipette. A drawback of such a method is that is not easy, especially for untrained or poorly trained personnel, to introduce a precisely metered dose into the pipette. The job requires experience and skill, and the risk of inaccuracies is great. For example, air bubbles may be drawn along when sucking up a dose, which air bubbles may lead to the volume of the mixing substance being sucked up deviating from the desired volume.
Another drawback is the fact that a precise transfer of the dose from the pipette to the container requires skill as well, and that moreover the viscosity of the fluid plays an important role. If a highly viscous fluid is to be introduced into a container by means of a pipette, there is a great risk of residual fluid remaining behind in the pipette. Residue may remain behind in particular in the conical outlet of a pipette via which the fluid is to be transferred to a container. It is not easy to mix this residue yet with the substance that is present in a container at a later stage.
Yet another drawback of the use of a pipette is the fact that a pipette is not suitable for storing or transporting a dose present therein of a substance that is to be transferred to a container. Consequently, the pipette cannot be used, for example, for supplying a dose of a specific substance that is not available as standard in a laboratory, for example.
The prior art therefore does not provide satisfactory methods and means for transferring a very precisely metered dose to a container without losing part of the dose (for example in the form of residue that remains behind in a pipette or assembly as described above).